Analytical and Bioanalytical Chemistry (v.410, #22)
Food safety analysis by Steven J. Lehotay (5329-5330).
is a Lead Scientist with the USDA Agricultural Research Service, which he joined after graduating with a PhD in Chemistry from the University of Florida in 1992. His research concerns many types of analytical techniques applied in novel and useful ways to address all aspects in the analysis of pesticides, veterinary drugs, and other contaminants in food. He is a Clarivate Analytics Highly Cited Researcher with >110 peer-reviewed publications, >220 abstracts, and >40 other scientific publications. His awards include the ACS-AGRO Award for Innovation in Chemistry of Agriculture, AOAC International Harvey W. Wiley Award, and numerous honors from the USDA.
Hits and misses in research trends to monitor contaminants in foods by Steven J. Lehotay; Yibai Chen (5331-5351).
Monitoring of chemicals of toxicological concern in food is commonly needed for many purposes, which include (in part) food safety, regulatory enforcement, risk assessment, international food trade, label claims, environmental protection, industry needs, academic research, and consumer confidence. Chemicals of current concern include a variety of toxins, pesticides, veterinary drugs, growth promoters, environmental contaminants, toxic metals, allergens, endocrine disruptors, genetically modified organisms, melamine, acrylamide, furans, nitrosamines, food additives, packaging components, and miscellaneous other chemicals. In light of past crises, the potential harm from known or unknown chemicals not currently monitored are a source of additional concern by the food industry, regulators, scientists, and consumers. As global food trade has expanded and detection techniques have improved, chemical contaminant analysis of foods has also increased in importance and activity. This critical review article is aimed to highlight current trends in the literature, including neglected research needs, on the analysis of chemicals of toxicological concern in foods. Graphical abstract
Keywords: Review; Food safety analysis; Chemical residues; Contaminants; Regulatory monitoring
Consumer-friendly food allergen detection: moving towards smartphone-based immunoassays by Georgina M. S. Ross; Monique G. E. G. Bremer; Michel W. F. Nielen (5353-5371).
In this critical review, we provide a comprehensive overview of immunochemical food allergen assays and detectors in the context of their user-friendliness, through their connection to smartphones. Smartphone-based analysis is centered around citizen science, putting analysis into the hands of the consumer. Food allergies represent a significant worldwide health concern and consumers should be able to analyze their foods, whenever and wherever they are, for allergen presence. Owing to the need for a scientific background, traditional laboratory-based detection methods are generally unsuitable for the consumer. Therefore, it is important to develop simple, safe, and rapid assays that can be linked with smartphones as detectors to improve user accessibility. Smartphones make excellent detection systems because of their cameras, embedded flash functions, portability, connectivity, and affordability. Therefore, this review has summarized traditional laboratory-based methods for food allergen detection such as enzyme-linked-immunosorbent assay, flow cytometry, and surface plasmon resonance, and the potential to modernize these methods by interfacing them with a smartphone readout system, based on the aforementioned smartphone characteristics. This is the first review focusing on smartphone-based food-allergen detection methods designed with the intention of being consumer-friendly. Graphical abstractA smartphone-based food allergen detection system in three easy steps (1) sample preparation, (2) allergen detection on a smartphone using antibodies, which then transmits the data wirelessly, (3) analytical results sent straight to smartphone
Keywords: Food allergen; Immunoassay; Smartphone; Consumer; Multiplex; Citizen science
Target screening of 105 veterinary drug residues in milk using UHPLC/ESI Q-Orbitrap multiplexing data independent acquisition by Jian Wang; Daniel Leung; Willis Chow; James Chang; Jon W. Wong (5373-5389).
has been working as a research scientist at the Calgary Laboratory with the Canadian Food Inspection Agency (CFIA) since 2002. His work focuses on method development and validation on analysis of chemical contaminant residues, including pesticides and veterinary drugs in food using emerging mass spectrometric technologies. He also develops statistical approaches to estimate measurement uncertainty based on method validation and quality control data using SAS program. is a science laboratory evaluator at the Calgary Laboratory, Canadian Food Inspection Agency, Canada. He studied and obtained his B.Sc. in Chemistry at the University of Alberta. Soon after graduation, he joined the Government of Canada. He has worked in the field of pesticide residue analysis for almost 30 years. When he is not working in the lab, he likes to ride his bike all over Canada and Europe. is a science laboratory evaluator working in the Calgary Laboratory Research and Development Unit of the Canadian Food Inspection Agency. His work focuses on the detection and quantification of pesticide residues in food by both unit mass and high resolution mass spectrometry. He has been with the agency since 2003. has worked with ThermoFisher Scientific since 2003. His duties include application and development of laboratory instruments (gas, high performance liquid chromatography, liquid chromatography-tandem mass spectrometry, ultra-fast GC, multidimensional GC, micro-flow ultrahigh performance liquid chromatography, tandem mass spectrometry, and high resolution/high accuracy mass spectrometry) for food and environmental analysis. He has had more than 25 years of experience in the operation of environmental laboratories as a manager and a Director. is a research chemist at the Center for Food Safety and Applied Nutrition, United States Food and Drug Administration in College Park, Maryland, USA. He has been with the FDA since 2002 and is involved in the development of multi-residue analytical methods for foods and other agricultural commodities. This paper presents a multi-class target screening method for the detection of 105 veterinary drug residues from 11 classes in milk using ultra-high performance liquid chromatography electrospray ionization quadrupole Orbitrap mass spectrometry (UHPLC/ESI Q-Orbitrap). The method is based on a non-target approach of full mass scan and multiplexing data-independent acquisition (Full MS/mDIA). The veterinary drugs include endectocides, fluoroquinolones, ionophores, macrolides, nitroimidazole, NSAIDs, β-lactams, penicillins, phenicols, sulfonamides, and tetracyclines. Veterinary drug residues were extracted from milk using a salting-out and solid-phase extraction (SOSPE) procedure, which entailed the precipitation of milk proteins by an extraction buffer (oxalic acid and EDTA, pH 3) and acetonitrile, a salting-out acetonitrile/water phase separation using ammonium sulfate, and solid-phase extraction for clean-up using polymeric reversed-phase sorbent cartridges. The Q-Orbitrap Full MS/dd-MS2 (data-dependent acquisition) was used to acquire product-ion spectra of individual veterinary drugs to build a compound database and a mass spectral library, whereas its Full MS/mDIA was utilized to acquire sample data from milk for target screening of veterinary drugs fortified at 1.0 or 10.0 μg/kg. The in-spectrum mass correction or solvent background lock-mass correction was used to minimize mass error when building the compound database from experimental dd-MS2 accurate mass data. Retention time alignment and response threshold adjustment were used to eliminate or reduce false negatives and/or false positive rates. The validated method was capable of screening 58% and 96% of 105 veterinary drugs at 1.0 and 10.0 μg/kg, respectively, without manually evaluating every compound during data processing, which will reduce the workload in routine practice.
Keywords: UHPLC/ESI Q-Orbitrap; Veterinary drug residues; Compound database; Target screening; Milk; Multiplexing data-independent acquisition
Elucidation of non-intentionally added substances migrating from polyester-polyurethane lacquers using automated LC-HRMS data processing by Elsa Omer; Ronan Cariou; Gérald Remaud; Yann Guitton; Hélène Germon; Paul Hill; Gaud Dervilly-Pinel; Bruno Le Bizec (5391-5403).
is a PhD candidate working on a collaborative project involving the LABERCA (Oniris - National Veterinary College of Nantes Atlantique, France), Ardagh Group (a global leader in packaging) and the CEISAM research team (University of Nantes, France). Her research interests lie in the analytical chemistry domain, with a focus on untargeted approaches dedicated to ensuring safety of food contact material. is a senior researcher and analytical chemist at LABERCA (Oniris - National Veterinary College of Nantes Atlantique, France). He has been focusing on chemical food safety issues for 15 years. He is in charge of research projects related to the transfer of persistent organic pollutants along the food chain, as well as compounds migrating from food contact materials, more specifically emerging compounds, using high-resolution mass spectrometry technologies. is the Head of the EBSI Team in CEISAM (UMR-CNRS 6230), University of Nantes, France. After obtaining a PhD in 1984 from Nantes University (France), he spent 3 years at the University of Uppsala (Sweden) developing NMR spectroscopy to study RNA and DNA fragments. He then worked as quality control manager in the industry. In 2003, he was recruited as a Professor at Nantes University. His research areas cover methodologies for authenticity control, counterfeiting detection, and forensic studies on natural products, food, medicines, and pollutants. is a research engineer and is responsible for the metabolomics/lipidomic platform of LABERCA (Oniris - National Veterinary College of Nantes Atlantique, France). He is a senior expert scientist in mass spectrometry-based (MS) omic profiling, related data processing, and statistical analysis, including bioinformatics and computing tools used for seeking useful information in MS fingerprints. At the French level, he is involved in the workflow4metabolomics infrastructure for reproducible and sharable data processing of metabolomics studies. He is also a member of the board of the French-speaking Metabolomics and Fluxomics Network (RFMF). is a chemist at the R&D center of Ardagh metal packaging. She is in charge of the characterization laboratory and the regulatory affairs. Her main goal daily is to ensure the best safety possible for the metal packaging supplied by the group. Her research interests are the applications of high resolution mass spectrometry in the NIAS risk assessment. is the R&D manager for lacquers at the Ardagh R&D center based in Crosmières, France. He is responsible for the qualification of new coatings, including their regulatory compliance. Understanding the nature of the species that can migrate from internal coatings is a key to this activity. Paul is active within trade associations making sure that the industry is aware of and reacts to regulatory developments at European and national levels. is a senior researcher at LABERCA (Oniris - National Veterinary College of Nantes Atlantique, France) where she acts as Scientific Advisor. Her research activity is devoted to chemical food safety issues and she is responsible for the management of research projects dealing with the modeling of contaminants transfer along the food chain and the evaluation of consumers chemical exposure. She has been working for several years on both targeted and untargeted analytical approaches to study the effects of chemical exposure and investigate related biomarkers, in a risk assessment perspective. is a Professor in chemical food safety at the National Veterinary College of Nantes Atlantique (Oniris, France). He is the Director of the Joint Research Unit no. 1329 Oniris-INRA and Head of the French National Reference Laboratory LABERCA in charge of a wide range of chemical hazards in food. Professor Le Bizec is the Head Deputy of the Doctoral School ‘Biology and Health’ of the Bretagne-Loire University. He has served as a member in the Contaminant panel of the French Agency for Food Safety (ANSES) since 2003, in a FAO/WHO Joint Expert Committee on Food Additives (JECFA) since 2008, and in IARC (in 2013). He has been a member of the World Antidoping Agency (WADA) Laboratory Expert Group since 2015. Bruno Le Bizec was bestowed Knight of the Order of Academic Palms in 2015 by the French Government for distinguished services. An untargeted strategy aiming at identifying non-intentionally added substances (NIAS) migrating from coatings was developed. This innovative approach was applied to two polyester-polyurethane lacquers, for which suppliers previously provided the identity of the monomers involved. Lacquers were extracted with acetonitrile and analyzed by liquid chromatography-high resolution mass spectrometry (LC-HRMS). Data, acquired in the full scan mode, were processed using an open-source R-environment (xcms and CAMERA packages) to list the detected features and deconvolute them in groups related to individual compounds. The most intense groups, accounting for more than 85% of cumulated feature intensities, were then investigated. A homemade database, populated with predicted polyester oligomer combinations from a relevant selection of diols and diacids, enabled highlighting the presence of 14 and 17 cyclic predicted polyester oligomers in the two lacquers, including three mutual combinations explained by common known monomers. Combination hypotheses were strengthened by chromatographic considerations and by the investigation of fragmentation patterns. Regarding unpredicted migrating substances, four monomers were hypothesised to explain several polyester or caprolactam oligomer series. Finally, considering both predicted and tentatively elucidated unpredicted oligomers, it was possible to assign hypotheses to features representing up to 82% and 90% of the cumulated intensities in the two lacquers, plus 9% and 3% (respectively) originating from the procedural blank. Graphical abstractElucidation of non-intentionally added substances
Keywords: Food contact material; Non-intentionally added substance; Oligomer; Untargeted approach; HRMS screening; Chemical food safety
Capillary electrophoresis–tandem mass spectrometry for multiclass analysis of polar marine toxins by Daniel G. Beach; Elliott S. Kerrin; Krista Thomas; Michael A. Quilliam; Pearse McCarron (5405-5420).
is a research officer with Measurement Science and Standards at National Research Council Canada in Halifax, Nova Scotia. His research focuses on the development of advanced mass spectrometry methods and reference materials for the analysis of marine and freshwater biotoxins in seafood and environmental samples. is a technical officer with Measurement Science and Standards at National Research Council Canada in Halifax, Nova Scotia. His expertise is in the development of analytical methods using liquid chromatography, tandem mass spectrometry, differential ion mobility spectrometry, and capillary electrophoresis. is a technical officer with Measurement Science and Standards at National Research Council Canada in Halifax, Nova Scotia. Her research at National Research Council Canada has focused on the isolation and analytical chemistry of biotoxins, and on the production of certified reference materials. is Researcher Emeritus with Measurement Science and Standards at National Research Council Canada and Adjunct Professor of Chemistry at Dalhousie University in Halifax, Nova Scotia. His research at National Research Council Canada has focused on analytical chemistry of environmental and food contaminants, particularly biotoxins, and on the production of certified reference materials. is a research officer and team leader with Measurement Science and Standards at National Research Council Canada in Halifax, Nova Scotia. His research has a metrology focus, including the development of analytical methods and the production of certified reference materials for algal biotoxins, with a particular interest in toxins relevant to seafood and water safety. Polar marine toxins are more challenging to analyze by mass spectrometry-based methods than lipophilic marine toxins, which are now routinely measured in shellfish by multiclass reversed-phase liquid chromatography–tandem mass spectrometry (MS/MS) methods. Capillary electrophoresis (CE)–MS/MS is a technique that is well suited for the analysis of polar marine toxins, and has the potential of providing very high resolution separation. Here, we present a CE–MS/MS method developed, with use of a custom-built interface, for the sensitive multiclass analysis of paralytic shellfish toxins, tetrodotoxins, and domoic acid in seafood. A novel, highly acidic background electrolyte (5 M formic acid) was designed to maximize protonation of analytes and to allow a high degree of sample stacking to improve the limits of detection. The method was applied to a wide range of regulated and less common toxin analogues, and exhibited a high degree of selectivity between toxin isomers and matrix interference. The limits of detection in mussel tissue were 0.0052 mg/kg for tetrodotoxins, 0.160 mg/kg for domoic acid, and between 0.0018 and 0.120 mg/kg for paralytic shellfish toxins, all of which showed good linearity. Minimal ionization suppression was observed when the response from neat and mussel-matrix-matched standards was corrected with multiple internal standards. Analysis of shellfish matrix reference materials and spiked samples demonstrated good accuracy and precision. Finally, the method was transferred to a commercial CE–MS/MS system to demonstrate its widespread applicability for use in both R & D and routine regulatory settings. The approach of using a highly acidic background electrolyte is of broad interest, and can be considered generally applicable to simultaneous analysis of other classes of small, polar molecules with differing pK a values. Graphical abstractᅟ
Keywords: Biotoxins; Tetrodotoxin; Paralytic shellfish poisoning; Domoic acid; Harmful algal bloom; Capillary electrophoresis
Selective labeling for the identification and semi-quantification of lipid aldehydes in food products by Boudewijn Hollebrands; Eftychia Varvaki; Sonja Kaal; Hans-Gerd Janssen (5421-5429).
Lipid oxidation reactions in foods rich in healthy unsaturated fatty acids result in the formation of a wide range of oxidation products that can have adverse effects on food quality and safety. To improve the understanding of oxidation reactions and methods for their inhibition, detailed information on the type and levels of the oxidation products formed is required. Accurate measurement of lipid oxidation products, especially of the non-volatile aldehyde products, has so far been a challenge due to the low sensitivity and limited specificity of most analytical methods. Here, a novel normal-phase LC method that uses selective labeling of aldehydes and epoxides with 7-(diethylamino)coumarin-3-carbohydrazide (CHH) is described. Labeling of alkanals is quantitative within 10 h. For alkenals, conversion is only around 50% at 24 h reaction time. Detailed MS identification of all aldehydes and epoxides is possible by using high-resolution MS and data-dependent MS2 acquisition. Fluorescence detection was successfully used to quantify groups of oxidation products. Sensitivity was high enough to allow accurate quantification even in fresh mayonnaises, where levels of around only 0.3 g total aldehydes/kg oil were found. Individual species can be quantified by MS if suitable reference standards are available. If no standards can be used, semi-quantification using an average response factor is an option. Clearly, the novel derivatization method is suitable for monitoring secondary lipid oxidation products in the early stages of shelf life. This makes it an important tool for developing improved food products. Graphical abstractSelective labeling of low and high molecular weight lipid oxidation products with 7-(diethylamino) coumarin-3-carbohydrazide for identification and semi-quantification
Keywords: Lipid oxidation; Semi-quantification; Aldehydes; Labeling; 7-(diethylamino)coumarin-3-carbohydrazide
Ultra turrax® tube drive for the extraction of pesticides from egg and milk samples by Julia Sturm; Peter Wienhold; Thomas Frenzel; Karl Speer (5431-5438).
The Ultra turrax® tube drive, already successfully applied for the extraction of plant materials, has also proved to be suitable for the analysis of pesticides in eggs and milk. In comparison to the matrix solid-phase dispersion (MSPD), the extraction is less time-consuming at excellent extraction efficiency. Further advantages are the flexibility of the extraction conditions with respect to the pH value and water activity. So, even strongly acidic pesticides such as phenoxy carboxylic acids can be extracted. Eighty-nine GC-amenable and 75 LC-amenable pesticides, which had been detected successfully in whole chicken eggs following MSPD extraction and further processing according to Hildmann et al., could also be analyzed with the modified method. In addition, the analysis spectrum could be expanded by 4 GC- and 37 LC-amenable substances. Of the 208 pesticides tested, 205 substances could be detected in whole chicken eggs. Similar excellent results were achieved for the milk matrix. Furthermore, the modified extraction method allows a determination of the fat content from the same analysis approach.
Keywords: Pesticides; Ultra turrax®tube drive; MSPD; Egg; Milk; GC-MS/MS; LC-MS/MS
Serogroup-level resolution of the “Super-7” Shiga toxin-producing Escherichia coli using nanopore single-molecule DNA sequencing by Adam Peritz; George C. Paoli; Chin-Yi Chen; Andrew G. Gehring (5439-5444).
DNA sequencing and other DNA-based methods are now broadly used for detection and identification of bacterial foodborne pathogens. For the identification of foodborne bacterial pathogens, taxonomic assignments must be made to the species or even subspecies level. Long-read DNA sequencing provides finer taxonomic resolution than short-read sequencing. Here, we demonstrate the potential of long-read shotgun sequencing obtained from the Oxford Nanopore Technologies (ONT) MinION single-molecule sequencer, in combination with the Basic Local Alignment Search Tool (BLAST) with custom sequence databases, for foodborne pathogen identification. A library of mixed DNA from strains of the “Super-7” Shiga toxin-producing Escherichia coli (STEC) serogroups (O26, O45, O103, O111, O121, O145, and O157[:H7]) was sequenced using the ONT MinION resulting in 44,245 long-read sequences. The ONT MinION sequences were compared to a custom database composed of the E. coli O-antigen gene clusters. A vast majority of the sequence reads were from outside of the O-antigen cluster and did not align to any sequences in the O-antigen database. However, 58 sequences (0.13% of the total sequence reads) did align to a specific Super-7 O-antigen gene cluster, with each O-antigen cluster aligning to at least four sequence reads. BLAST analysis against a custom whole-genome database revealed that 5096 (11.5%) of the MinION sequence reads aligned to one and only one sequence in the database, of which 99.6% aligned to a sequence from a “Super-7” STEC. These results demonstrate the ability of the method to resolve STEC to the serogroup level and the potential general utility of the MinION for the detection and typing of foodborne pathogens.
Keywords: MinION; Nanopore DNA sequencing; Shiga toxin-producing E. coli, STEC; Foodborne pathogen detection
Rapid detection and differentiation of Staphylococcus colonies using an optical scattering technology by Tawfiq S. Alsulami; Xingyue Zhu; Maha Usama Abdelhaseib; Atul K. Singh; Arun K. Bhunia (5445-5454).
Staphylococcus species are a major pathogen responsible for nosocomial infections and foodborne illnesses. We applied a laser-based BARDOT (bacterial rapid detection using optical scattering technology) for rapid colony screening and detection of Staphylococcus on an agar plate and differentiate these from non-Staphylococcus spp. Among the six growth media tested, phenol red mannitol agar (PRMA) was found most suitable for building the Staphylococcus species scatter image libraries. Scatter image library for Staphylococcus species gave a high positive predictive value (PPV 87.5–100%) when tested against known laboratory strains of Staphylococcus spp., while the PPV against non-Staphylococcus spp. was 0–38%. A total of nine naturally contaminated bovine raw milk and ready-to-eat chicken salad samples were tested, and BARDOT detected Staphylococcus including Staphylococcus aureus with 80–100% PPV. Forty-five BARDOT-identified bacterial isolates from naturally contaminated foods were further confirmed by tuf and nuc gene-specific PCR and 16S rRNA gene sequence. This label-free, non-invasive on-plate colony screening technology can be adopted by the food industries, biotechnology companies, and public health laboratories for Staphylococcus species detection including S. aureus from various samples for food safety and public health management. Graphical abstract
Keywords: Optical sensor; BARDOT; Staphylococcus ; Food sample; 16S RNA gene
Label-free screening of foodborne Salmonella using surface plasmon resonance imaging by Jing Chen; Bosoon Park (5455-5464).
It is estimated that 95% of the foodborne infections are caused by 15 major pathogens. Therefore, rapid and effective multiplex screening techniques for these pathogens with improved efficiencies could benefit public health at lower costs. Surface plasmon resonance imaging (SPRi) provides a label-free, multiplex analytical platform for pathogen screening. In this study, we have developed a singleplex immunoassay for Salmonella to evaluate the potential of SPRi in pathogen detection. Anti-Salmonella and control ligands were arrayed onto the SPRi sensor chip in a microarray format. The influences of ligand immobilization pH and concentration were optimized, and a pause flow protocol was adopted to improve assay rapidity and sensitivity. The method shows good specificity against 6 non-Salmonella species and was able to detect 5 of 6 Salmonella serotypes, including 3 serotypes most frequently associated with outbreaks. Limits of detection were found to be 2.1 × 106 CFU/mL in phosphate-buffered saline and 7.6 × 106 CFU/mL in the presence of chicken rinse matrix with 8.9 × 107 CFU/mL of indigenous microflora. The condition of antibody array regeneration was optimized for sequential sample injections. Finally, the SPRi immunoassay was used to detect Salmonella directly from artificially spiked chicken carcass rinse samples. As low as 6.8 CFU/mL of Salmonella could be detected after overnight enrichment in buffered peptone water, demonstrating the potential in streamlined pathogen screening with minimal sample preparation and without detection labels. Graphical abstractᅟ
Keywords: Surface plasmon resonance imaging; Salmonella ; Foodborne pathogen; Label-free detection; Chicken rinsate; Food safety
Use of a quality control approach to assess measurement uncertainty in the comparison of sample processing techniques in the analysis of pesticide residues in fruits and vegetables by Steven J. Lehotay; Lijun Han; Yelena Sapozhnikova (5465-5479).
In routine monitoring of foods, reduction of analyzed test portion size generally leads to higher sample throughput, less labor, and lower costs of monitoring, but to meet analytical needs, the test portions still need to accurately represent the original bulk samples. With the intent to determine minimal fit-for-purpose sample size, analyses were conducted for up to 93 incurred and added pesticide residues in 10 common fruits and vegetables processed using different sample comminution equipment. The commodities studied consisted of apple, banana, broccoli, celery, grape, green bean, peach, potato, orange, and squash. A Blixer® was used to chop the bulk samples at room temperature, and test portions of 15, 10, 5, 2, and 1 g were taken for analysis (n = 4 each). Additionally, 40 g subsamples (after freezing) were further comminuted using a cryomill device with liquid nitrogen, and test portions of 5, 2, and 1 g were analyzed (n = 4 each). Both low-pressure gas chromatography-tandem mass spectrometry (LPGC-MS/MS) and ultrahigh-performance liquid chromatography (UHPLC)-MS/MS were used for analysis. An empirical approach was followed to isolate and estimate the measurement uncertainty contribution of each step in the overall method by adding quality control spikes prior to each step. Addition of an internal standard during extraction normalized the sample preparation step to 0% error contribution, and coefficients of variation (CVs) were 6–7% for the analytical steps (LC and GC) and 6–9% for the sample processing techniques. In practice, overall CVs averaged 9–11% among the different analytes, commodities, batches, test portion weights, and analytical and sample processing methods. On average, CVs increased up to 4% and bias 8–12% when using 1–2 g test portions vs. 10–15 g. Graphical abstractEfficient quality control approach to include sample processing
Keywords: Sample processing; Comminution; Measurement uncertainty; Pesticide residues analysis; Fruits and vegetables
Compensation for matrix effects in GC analysis of pesticides by using cucumber extract by Hyeyoung Kwon; Michelangelo Anastassiades; Daniela Dörk; Su-Myoung Hong; Byeong-Chul Moon (5481-5489).
Matrix effects (MEs) can adversely affect quantification in pesticide residue analysis using GC. Analyte protectants (APs) can effectively interact with and mask active sites in the GC system, and are added individually or in combination to sample extracts and calibration solutions to minimize errors related to MEs. Unfortunately, APs cannot sufficiently compensate for MEs in all cases. Plant extracts, containing a broad range of natural compounds with AP properties, can also be used for this purpose. In this study, the applicability of cucumber extract as a natural AP mixture was investigated both alone and in combination with traditional APs. Extracts of two selected difficult matrices (onion and garlic) were prepared according to the citrate-buffered QuEChERS (quick, easy, cheap, effective, rugged, and safe) procedure. ME values of 40 representative GC-amenable pesticides were compared when calibrating against standards in pure solvent and in cucumber extract, with and without the addition of APs. Using a GC system with a contaminated inlet liner, the use of a cucumber-based calibration solution decreased MEs remarkably. The combination of APs with cucumber raw extract further decreased MEs, resulting in more than 85% of the tested pesticides showing ≤ 10% ME in onion and ≤ 20% ME in garlic. These results demonstrate that the preparation of calibration standards based on cucumber extracts (with or without the addition of APs) is a very useful and practical approach to compensate for MEs in pesticide residue analysis using QuEChERS and GC-MS/MS. The use of various internal standards is furthermore critically discussed.
Keywords: Pesticide residue analysis; QuEChERS; Matrix effects; GC-MS/MS; Matrix-based calibration; Internal standard
Further improvements in pesticide residue analysis in food by applying gas chromatography triple quadrupole mass spectrometry (GC-QqQ-MS/MS) technologies by Elena Hakme; Ana Lozano; Samanta Uclés; Amadeo R. Fernández-Alba (5491-5506).
Nowadays, the control of pesticide residues in food is well established. The capacity of triple quadrupole technology to satisfy the current food regulations has been demonstrated. However, the permanent high demand of consumers for more sensitive and faster testing is driving the development of improved analytical methodologies that increase the performances of sensitivity and robustness and reduce the analysis time. In this work, the feasibility of decreasing the run time to 12.4 min by modifying the oven temperature program, for a multiresidue method covering 203 pesticides, was evaluated. Satisfactory sensitivity results were achieved by reaching a limit of quantitation of 2 μg kg−1 for a great variety of fruits and vegetables. The validated method based on updated GC-QqQ-MS/MS has confirmed the abovementioned challenges with adequate robustness by its application to routine analyses for 69 real samples. The proposed method can represent great benefit for laboratories as it allows increasing samples throughput. It is also very useful for risk assessment studies, where the needs of low reporting limits and very wide analytical scope are necessary.
Keywords: Fast GC-MS/MS analysis; Low reporting limits; Multiresidue method; Method validation
Pesticide analysis by pulsed flow modulation GCxGC-MS with Cold EI—an alternative to GC-MS-MS by Uri Keshet; Paulina Goldshlag; Aviv Amirav (5507-5519).
We explored the use of pulsed flow modulation (PFM) two-dimensional comprehensive gas chromatography (GCxGC) mass spectrometry with supersonic molecular beams (SMB) (also named Cold electron ionization (EI)) for achieving universal pesticide analysis in agricultural products. The use of GCxGC serves as an alternative to MS-MS in the needed reduction of matrix interference while enabling full-scan MS operation for universal pesticide analysis with reduced number of false negatives. Matrix interference is further reduced with Cold EI in view of the enhancement of the molecular ions. Pulsed flow modulation is a simple GCxGC modulator that does not consume cryogenic gases while providing tuneable second GCxGC column injection time for enabling the use of quadrupole-based mass spectrometry regardless its limited scanning speed. PFM-GCxGC-MS with Cold EI combines improved separation of GCxGC with Cold EI benefits of tailing-free ultra-fast ion source response time and enhanced molecular ions for the provision of increased sample identification information and reduced matrix interference. Consequently, PFM GCxGC-MS with Cold EI also improved NIST library identification probabilities of the spiked pesticides. PFM GCxGC is further characterized by largely increased second column sample and matrix capacity that as a result performs much better than thermal modulation GCxGC-MS with standard EI in the suppression of matrix interference. In a comparison with standard GC-MS, we measured with PFM GCxGC-MS with Cold EI an average total ion count matrix interference reduction factor of 32 for 12 pesticides in two matrices of baby leaves mixture and lettuce. In addition, Cold EI further increases the range of pesticides amenable for GC-MS analysis and its response is relatively uniform hence with it the need for pesticides specific calibration is reduced. Graphical abstractPulsed flow modulation GCxGC-MS with Cold EI significantly reduces matrix interference and improves sample identification.
Keywords: Pulsed flow modulation; GCxGC; GCxGC-MS; Supersonic molecular beams; Cold EI; Pesticide analysis
Method development and validation for total haloxyfop analysis in infant formulas and related ingredient matrices using liquid chromatography-tandem mass spectrometry by Urairat Koesukwiwat; Lukas Vaclavik; Katerina Mastovska (5521-5528).
According to the European Commission directive 2006/141/EC, haloxyfop residue levels should not exceed 0.003 mg/kg in ready-to-feed infant formula, and the residue definition includes sum of haloxyfop, its esters, salts, and conjugates expressed as haloxyfop. A simple method for total haloxyfop analysis in infant formula and related ingredient matrices was developed and validated using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The sample preparation consisted of an alkaline hydrolysis with methanolic sodium hydroxide to release haloxyfop (parent acid) from its bound forms prior to the extraction with acetonitrile. A mixture of magnesium sulfate (MgSO4) and sodium chloride (NaCl) (4:1, w/w) was added to the extract to induce phase separation and force the analyte into the upper acetonitrile-methanol layer and then a 1-mL aliquot was subsequently cleaned up by dispersive solid phase extraction with 150 mg of MgSO4 and 50 mg of octadecyl (C18) sorbent. The analytical procedure was developed and carefully optimized to enable low-level, total haloxyfop analysis in a variety of challenging matrices, including infant formulas and their important high-carbohydrate, high-protein, high-fat, and emulsifier ingredients. The final method was validated in two different laboratories by fortifying samples with haloxyfop and haloxyfop-methyl, which was used as a model compound simulating bound forms of the analyte. Mean recoveries of haloxyfop across all fortification levels and evaluated matrices ranged between 92.2 and 114% with repeatability, within-lab reproducibility, and reproducibility RSDs ≤ 14%. Based on the validation results, this method was capable to convert the haloxyfop ester into the parent acid in a wide range of sample types and to reliably identify and quantify total haloxyfop at the target 0.003 mg/kg level in infant formulas (both powdered and ready-to-feed liquid forms). Graphical abstractLC-MS/MS-based workflow for the determination of the total haloxyfop in infant formula and related ingredients
Keywords: Pesticides; Phenoxy acid herbicides; Alkaline hydrolysis; QuEChERS; Infant formula; Liquid chromatography-tandem mass spectrometry
Application and evaluation of a high-resolution mass spectrometry screening method for veterinary drug residues in incurred fish and imported aquaculture samples by Sherri B. Turnipseed; Joseph M. Storey; I-Lin Wu; Charles M. Gieseker; Nicholas R. Hasbrouck; Tina C. Crosby; Wendy C. Andersen; Shanae Lanier; Christine R. Casey; Robert Burger; Mark R. Madson (5529-5544).
The ability to detect chemical contaminants, including veterinary drug residues in animal products such as fish, is an important example of food safety analysis. In this paper, a liquid chromatography high-resolution mass spectrometry (LC-HRMS) screening method using a quadrupole-Orbitrap instrument was applied to the analysis of veterinary drug residues in incurred tissues from aquacultured channel catfish, rainbow trout, and Atlantic salmon and imported aquacultured products including European eel, yellow croaker, and tilapia. Compared to traditional MS methods, the use of HRMS with nontargeted data acquisition and exact mass measurement capability greatly increased the scope of compounds that could be monitored simultaneously. The fish samples were prepared for analysis using a simple efficient procedure that consisted of an acidic acetonitrile extraction followed by solid phase extraction cleanup. Two different HRMS acquisition programs were used to analyze the fish extracts. This method detected and identified veterinary drugs including quinolones, fluoroquinolones, avermectins, dyes, and aminopenicillins at residue levels in fish that had been dosed with those compounds. A metabolite of amoxicillin, amoxicillin diketone, was also found at high levels in catfish, trout, and salmon. The method was also used to characterize drug residues in imported fish. In addition to confirming findings of fluoroquinolone and sulfonamide residues that were found by traditional targeted MS methods, several new compounds including 2-amino mebendazole in eel and ofloxacin in croaker were detected and identified. Graphical AbstractAquacultured samples are analyzed with a high-resolution mass spectrometry screening method to detect and identify unusual veterinary drug residues including ofloxacin in an imported fish.
Keywords: High-resolution mass spectrometry; Screening method; Veterinary drug residues
Multiclass screening of >200 pharmaceutical and other residues in aquatic foods by ultrahigh-performance liquid chromatography–quadrupole-Orbitrap mass spectrometry by Cong Kong; Yang Wang; Yuanfei Huang; Huijuan Yu (5545-5553).
A quick screening method of more than 200 pharmaceutical and other residues in aquatic foods based on ultrahigh-performance liquid chromatography–quadrupole-Orbitrap mass spectrometry (UHPLC-Q/Orbitrap MS) was established. In this method, after the addition of 200 μL of 1 M EDTA-Na2, 2 g of each sample homogenate was extracted successively with 10 mL of acetonitrile and 10 mL of ethyl acetate. The extracts were combined, dried under nitrogen flow, and redissolved in 0.1% formic acid in acetonitrile/water (4:6, v/v) for analysis. The prepared samples were analyzed by UHPLC- Q/Orbitrap MS system in Full MS/ddMS2 (full-scan data-dependent MS/MS) mode. Compound identification was performed through comparison of the sample data with the database for standard chemicals, including the retention time, precursor ion, product ions, and isotope pattern for all 206 compounds. Five different aquatic food matrices (carp, shrimp, crab, eel, and mussel) spiked with the analytes at 1, 10, and 50 ng/g were evaluated to assess recoveries, precision, matrix effects, stability, and detection limits using the method. UHPLC analyses required 25 min, and 178–200 analytes met identification criteria at 50 ng/g depending on the matrix. Furthermore, practical application of this method for real samples displayed strong screening capability. Graphical abstractA quick screening method of >200 pharmaceutical and other residues in aquatic foods based on ultrahighperformance liquid chromatography–quadrupole-Orbitrap mass spectrometer was established. Fivedifferent aquatic food matrices, including carp, shrimp, crab, eel and mussel, were studied to evaluatescreen limit at 1, 10 and 50 μg·kg-1 level. Results suggest the high reliability, high time-efficiency and goodsimplicity of the method.
Keywords: Veterinary drug; Aquatic food; Screening; Orbitrap; Pesticide; Contaminant residue
Simultaneous determination of amantadine and rimantadine in feed by liquid chromatography-Qtrap mass spectrometry with information-dependent acquisition by Qi Jia; Dan Li; Xinlu Wang; Shuming Yang; Yongzhong Qian; Jing Qiu (5555-5565).
A sensitive method for simultaneous determination of amantadine and rimantadine in feed was developed using an ultra-high-performance liquid chromatography-triple quadrupole linear ion trap mass spectrometry (UHPLC-Qtrap-MS) in the multiple reaction monitoring information-dependent acquisition-enhanced product ion (MRM-IDA-EPI) mode, and employing the mixed cation exchange (MCX) solid-phase extraction column as sample cleanup and amantadine-d15 and rimantadine-d4 as internal standards, respectively. Compared to traditional MRM mode, for the targeted drugs in feed simultaneously both the secondary mass spectra and MRM information can be obtained using UHPLC-Qtrap-MS with MRM-IDA-EPI mode, and thus more accurate qualitative confirmation results achieved even at lower concentration of 0.2 μg/L in acceptable purity fit values. After optimization of sample preparation, good linearities (R > 0.9994) were obtained over the concentration range from 1 to 200 μg/L for amantadine and rimantadine. The precision was validated by intra-day and inter-day, and the relative standard deviations were all within 9.61%. Mean recoveries ranged from 76.1 to 112% at spiked concentrations of 0.5–100 μg/kg in three types of feed samples, including formula feed and complex concentrated feed for pigs and premix feed for chicken. The limits of detection (LODs) and quantification (LOQs) were 0.2 and 0.5 μg/kg for both drugs, respectively. The application in real feed samples further proved the accuracy and reliability of the developed method. This method provides an important tool to detect illegal uses of amantadine and rimantadine in feed. Graphical abstractSimultaneous quantitation and qualitative confirmation of amantadine and rimantadine in feed by MRM-IDA-EPI
Keywords: Amantadine; Rimantadine; Feed; Solid-phase extraction; Liquid chromatography-triple Qtrap mass spectrometry
In-house validation of a rapid and efficient procedure for simultaneous determination of ergot alkaloids and other mycotoxins in wheat and maize by Natalia Arroyo-Manzanares; Karl De Ruyck; Valdet Uka; Laura Gámiz-Gracia; Ana M. García-Campaña; Sarah De Saeger; José Diana Di Mavungu (5567-5581).
A fundamental step in addressing the global problem of mycotoxins is the development of highly sensitive, multi-class extraction and detection methods. This constitutes a field of research that has in recent years enjoyed a steady advance. Such methods, generally based on liquid chromatography coupled to mass spectrometry, are widely reported successfully detecting various mycotoxins in different food and feed samples. In this work, an innovative approach to multi-class mycotoxin control is proposed, offering specific advantages: a broader inclusion of more mycotoxin classes, robust and thorough extraction for all target compounds despite their varied chemical properties, and determination of all analytes from a single injection. The method involved the extraction and quantification of the main mycotoxins produced by Aspergillus, Fusarium, and Penicillium fungi, as well as their reported derivatives, together with 12 other compounds most commonly produced by Claviceps purpurea. The popularly reported QuEChERS technique has been reduced to a simple “salting-out liquid-liquid extraction” (SO-LLE) to obtain the most efficient extraction of the aforementioned mycotoxin classes in a very short time. This is in particular extremely important in ensuring correct determination of individual ergot alkaloids, for which short and robust sample preparation as well as short analytical sequences were key for minimizing the epimerization during analysis. The analyses of wheat and maize samples were performed using ultra-high performance liquid chromatography coupled with tandem mass spectrometry. Matrix-matched calibration curves were established and limits of quantification were below the maximum levels established by the EU regulation. The precision (repeatability and intermediate precision) was lower than 13% in all cases and recoveries ranged between 60 and 98% in maize and between 62 and 103% in wheat, fulfilling the current legislation. The method was applied to study the co-occurrence of these mycotoxins in wheat (n = 13) and maize (n = 15) samples from six European countries. A successful quantification of 23 different mycotoxins, from all major classes, in 85% of wheat and 93% of maize samples was achieved.
Keywords: Mycotoxins; Co-occurrence; Cereals; Ultra-high performance liquid chromatography; Mass spectrometry; QuEChERS; SO-LLE
Identification of acetylated derivatives of zearalenone as novel plant metabolites by high-resolution mass spectrometry by Laura Righetti; Luca Dellafiora; Daniele Cavanna; Enrico Rolli; Gianni Galaverna; Renato Bruni; Michele Suman; Chiara Dall’Asta (5583-5592).
Zearalenone (ZEN) major biotransformation pathways described so far are based on glycosylation and sulfation, although acetylation of trichothecenes has been reported as well. We investigated herein the ZEN acetylation metabolism route in micropropagated durum wheat leaf, artificially contaminated with ZEN. We report the first experimental evidence of the formation of novel ZEN acetylated forms in wheat, attached both to the aglycone backbone as well as on the glucose moiety. Thanks to the advantages provided by high-resolution mass spectrometry, identification and structure annotation of 20 metabolites was achieved. In addition, a preliminary assessment of the toxicity of the annotated metabolites was performed in silico focusing on the toxicodynamic of ZEN group toxicity. All the metabolites showed a worse fitting within the estrogen receptor pocket in comparison with ZEN. Nevertheless, possible hydrolysis to the respective parent compounds (i.e., ZEN) may raise concern from the health perspective because these are well-known xenoestrogens. These results further enrich the biotransformation profile of ZEN, providing a helpful reference for assessing the risks to animals and humans. Graphical abstractᅟ
Keywords: Food safety; Masked mycotoxins; Acetylation; Plant biotransformation
Non-targeted analysis of unexpected food contaminants using LC-HRMS by Marco Kunzelmann; Martin Winter; Magnus Åberg; Karl-Erik Hellenäs; Johan Rosén (5593-5602).
A non-target analysis method for unexpected contaminants in food is described. Many current methods referred to as “non-target” are capable of detecting hundreds or even thousands of contaminants. However, they will typically still miss all other possible contaminants. Instead, a metabolomics approach might be used to obtain “true non-target” analysis. In the present work, such a method was optimized for improved detection capability at low concentrations. The method was evaluated using 19 chemically diverse model compounds spiked into milk samples to mimic unknown contamination. Other milk samples were used as reference samples. All samples were analyzed with UHPLC-TOF-MS (ultra-high-performance liquid chromatography time-of-flight mass spectrometry), using reversed-phase chromatography and electrospray ionization in positive mode. Data evaluation was performed by the software TracMass 2. No target lists of specific compounds were used to search for the contaminants. Instead, the software was used to sort out all features only occurring in the spiked sample data, i.e., the workflow resembled a metabolomics approach. Procedures for chemical identification of peaks were outside the scope of the study. Method, study design, and settings in the software were optimized to minimize manual evaluation and faulty or irrelevant hits and to maximize hit rate of the spiked compounds. A practical detection limit was established at 25 μg/kg. At this concentration, most compounds (17 out of 19) were detected as intact precursor ions, as fragments or as adducts. Only 2 irrelevant hits, probably natural compounds, were obtained. Limitations and possible practical use of the approach are discussed.
Keywords: Non-targeted analysis; Food contaminants; Food safety; HRMS; LC-MS; Unknown analysis
Detection of nanoplastics in food by asymmetric flow field-flow fractionation coupled to multi-angle light scattering: possibilities, challenges and analytical limitations by Manuel Correia; Katrin Loeschner (5603-5615).
We tested the suitability of asymmetric flow field-flow fractionation (AF4) coupled to multi-angle light scattering (MALS) for detection of nanoplastics in fish. A homogenized fish sample was spiked with 100 nm polystyrene nanoparticles (PSNPs) (1.3 mg/g fish). Two sample preparation strategies were tested: acid digestion and enzymatic digestion with proteinase K. Both procedures were found suitable for degradation of the organic matrix. However, acid digestion resulted in large PSNPs aggregates/agglomerates (> 1 μm). The presence of large particulates was not observed after enzymatic digestion, and consequently it was chosen as a sample preparation method. The results demonstrated that it was possible to use AF4 for separating the PSNPs from the digested fish and to determine their size by MALS. The PSNPs could be easily detected by following their light scattering (LS) signal with a limit of detection of 52 μg/g fish. The AF4-MALS method could also be exploited for another type of nanoplastics in solution, namely polyethylene (PE). However, it was not possible to detect the PE particles in fish, due to the presence of an elevated LS background. Our results demonstrate that an analytical method developed for a certain type of nanoplastics may not be directly applicable to other types of nanoplastics and may require further adjustment. This work describes for the first time the detection of nanoplastics in a food matrix by AF4-MALS. Despite the current limitations, this is a promising methodology for detecting nanoplastics in food and in experimental studies (e.g., toxicity tests, uptake studies). Graphical abstractBasic concept for the detection of nanoplastics in fish by asymmetric flow field-flow fractionation coupled to multi-angle light scattering
Keywords: Nanoplastics; Asymmetric flow field-flow fractionation; Nanoparticles; Multi-angle light scattering; Enzymatic digestion
Determination of phthalic acid esters in different baby food samples by gas chromatography tandem mass spectrometry by Bárbara Socas-Rodríguez; Javier González-Sálamo; Antonio V. Herrera-Herrera; Álvaro Santana-Mayor; Javier Hernández-Borges (5617-5628).
In this work, a new method has been developed for the determination of 14 phthalic acid esters (i.e., benzylbutyl phthalate (BBP), bis-2-n-butoxyethyl phthalate (DBEP), dibutyl phthalate (DBP), dicyclohexyl phthalate (DCHP), bis-2-ethoxyethyl phthalate (DEEP), diethyl phthalate (DEP), diisodecyl phthalate (DIDP), diisononyl phthalate (DINP), bis-isopentyl phthalate (DIPP), bis (2-methoxyethyl) phthalate (DMEP), dimethyl phthalate (DMP), di-n-octyl phthalate (DNOP), bis-n-pentyl phthalate (DNPP), dipropyl phthalate (DPP)) and one adipate (bis (2-ethylhexyl) adipate (DEHA)) in different baby foods. Separation was carried out by gas chromatography triple quadrupole tandem mass spectrometry while the previous extraction of the samples was carried out using the QuEChERS method. The methodology was validated for four baby food samples (two fruit compotes of different compositions and two meat and fish purees with vegetables) using dibutyl phthalate-3,4,5,6-d4 (DBP-d4) as internal standard. Determination coefficients (R 2) of matrix-matched calibration curves were above 0.9922 in all cases while relative recovery values ranged between 70 and 120%, with relative standard deviation values below 19%. The limits of quantification of the method ranged between 0.03 and 1.11 μg/kg. Finally, the analysis of commercially available samples was carried out finding the presence of BBP, DEHA, DEP, DIDP, and DPP in some of the studied samples.
Keywords: Phthalic acid esters; Baby foods; QuEChERS; Gas chromatography; Tandem mass spectrometry
Analysis of a variety of inorganic and organic additives in food products by ion-pairing liquid chromatography coupled to high-resolution mass spectrometry by Anton Kaufmann; Mirjam Widmer; Kathryn Maden; Patrick Butcher; Stephan Walker (5629-5640).
A reversed-phase ion-pairing chromatographic method was developed for the detection and quantification of inorganic and organic anionic food additives. A single-stage high-resolution mass spectrometer (orbitrap ion trap, Orbitrap) was used to detect the accurate masses of the unfragmented analyte ions. The developed ion-pairing chromatography method was based on a dibutylamine/hexafluoro-2-propanol buffer. Dibutylamine can be charged to serve as a chromatographic ion-pairing agent. This ensures sufficient retention of inorganic and organic anions. Yet, unlike quaternary amines, it can be de-charged in the electrospray to prevent the formation of neutral analyte ion-pairing agent adducts. This process is significantly facilitated by the added hexafluoro-2-propanol. This approach permits the sensitive detection and quantification of additives like nitrate and mono-, di-, and triphosphate as well as citric acid, a number of artificial sweeteners like cyclamate and aspartame, flavor enhancers like glutamate, and preservatives like sorbic acid. This is a major advantage, since the currently used analytical methods as utilized in food safety laboratories are only capable in monitoring a few compounds or a particular category of food additives. Graphical abstractDeptotonation of ion pair agent in the electrospray interface
Keywords: Anionic food additives; Food safety; Ion-pairing chromatography; High-resolution mass spectrometry; Orbitrap
Analysis of unauthorized Sudan dyes in food by high-performance thin-layer chromatography by Wolfgang Schwack; Elodie Pellissier; Gertrud Morlock (5641-5651).
Food authenticity and food safety are of high importance to organizations as well as to the food industry to ensure an accurate labeling of food products. Respective analytical methods should provide a fast screening and a reliable cost-efficient quantitation. HPTLC was pointed out as key analytical technique in this field. A new HPTLC method applying caffeine-impregnated silica gel plates was developed for eight most frequently found fat-soluble azo dyes unauthorizedly added to spices, spice mixtures, pastes, sauces, and palm oils. A simple post-chromatographic UV irradiation provided an effective sample cleanup, which took 4 min for up to 46 samples in parallel. The method was trimmed to enable 23 simultaneous separations within 20 min for quantitation or 46 separations within 5 min for screening. Linear (4–40 ng/band) or polynomial (10–200 ng/band) calibrations of the eight azo dyes revealed high correlation coefficients and low standard deviations. Limits of detection and quantification were determined to be 2–3 and 6–9 ng/zone, respectively. After an easy sample extraction, recoveries of 70–120% were obtained from chili, paprika, and curcuma powder as well as from chili sauce, curry paste, and palm oil spiked at low (mainly 25–50 mg/kg) and high levels (150–300 mg/kg). For unequivocal identification, the compound in a suspect zone was eluted via a column into the mass spectrometer. This resulted in the hyphenation HPTLC-vis-HPLC-DAD-ESI-MS. Graphical abstractSimplified clean-up by UV irradiation for Sudan dye analysis in food by HPTLC-vis-HPLC-DAD-ESI-MS.
Keywords: Sudan dyes; High-performance thin-layer chromatography (HPTLC); HPTLC–mass spectrometry
In house validation of a high resolution mass spectrometry Orbitrap-based method for multiple allergen detection in a processed model food by Rosa Pilolli; Elisabetta De Angelis; Linda Monaci (5653-5662).
In recent years, mass spectrometry (MS) has been establishing its role in the development of analytical methods for multiple allergen detection, but most analyses are being carried out on low-resolution mass spectrometers such as triple quadrupole or ion traps. In this investigation, performance provided by a high resolution (HR) hybrid quadrupole-Orbitrap™ MS platform for the multiple allergens detection in processed food matrix is presented. In particular, three different acquisition modes were compared: full-MS, targeted-selected ion monitoring with data-dependent fragmentation (t-SIM/dd2), and parallel reaction monitoring. In order to challenge the HR-MS platform, the sample preparation was kept as simple as possible, limited to a 30-min ultrasound-aided protein extraction followed by clean-up with disposable size exclusion cartridges. Selected peptide markers tracing for five allergenic ingredients namely skim milk, whole egg, soy flour, ground hazelnut, and ground peanut were monitored in home-made cookies chosen as model processed matrix. Timed t-SIM/dd2 was found the best choice as a good compromise between sensitivity and accuracy, accomplishing the detection of 17 peptides originating from the five allergens in the same run. The optimized method was validated in-house through the evaluation of matrix and processing effects, recoveries, and precision. The selected quantitative markers for each allergenic ingredient provided quantification of 60–100 μgingred/g allergenic ingredient/matrix in incurred cookies.
Keywords: High resolution mass spectrometry; Multi-allergen detection; Processed matrix; Incurred samples; Peptide marker; In house validation
Through-packaging analysis of butter adulteration using line-scan spatially offset Raman spectroscopy by Santosh Lohumi; Hoonsoo Lee; Moon S. Kim; Jianwei Qin; Byoung-Kwan Cho (5663-5673).
Spectroscopic techniques for food quality analysis are limited to surface inspections and are highly affected by the superficial layers (skin or packaging material) of the food samples. The ability of spatially offset Raman spectroscopy (SORS) to obtain chemical information from below the surface of a sample makes it a promising candidate for the non-destructive analysis of the quality of packaged food. In the present study, we developed a line-scan SORS technique for obtaining the Raman spectra of packaged-food samples. This technique was used to quantify butter adulteration with margarine through two different types of packaging. Further, the significant commercial potential of the developed technique was demonstrated by its being able to discriminate between ten commercial varieties of butter and margarine whilst still in their original, unopened packaging. The results revealed that, while conventional backscattering Raman spectroscopy cannot penetrate the packaging, thus preventing its application to the quality analysis of packaged food, SORS analysis yielded excellent qualitative and quantitative analyses of butter samples. The partial least-square regression analysis predictive values for the SORS data exhibit correlation coefficient values of 0.95 and 0.92, associated with the prediction error 3.2 % and 3.9 % for cover-1 & 2, respectively. The developed system utilizes a laser line (ca. 14-cm wide) that enables the simultaneous collection of a large number of spectra from a sample. Thus, by averaging the spectra collected for a given sample, the signal-to-noise ratio of the final spectrum can be enhanced, which will then have a significant effect on the multivariate data analysis methods used for qualitative and/or qualitative analyses. This recently presented line-scan SORS technique could be applied to the development of high-throughput and real-time analysis techniques for determining the quality and authenticity various packaged agricultural products.
Keywords: Food safety; Food authenticity; Through-packaging analysis; Raman imaging; SORS
Speciation analysis of arsenic in seafood and seaweed: Part I—evaluation and optimization of methods by Mesay Mulugeta Wolle; Sean D. Conklin (5675-5687).
Several extraction and chromatographic methods were evaluated to identify optimum conditions for arsenic speciation analysis in seafood and seaweed. The extraction systems, which include aqueous, aqueous-organic, acidic, basic, and enzymatic solutions, were examined for their efficiency in extracting arsenic from finfish, crustaceans, molluscs, and seaweed keeping the chemical forms of the native arsenicals intact. While dilute solutions of nitric acid, hydrochloric acid, and tetramethylammonium hydroxide (TMAH) extract high fractions of arsenic from most of the matrices, the extractants oxidized arsenite (As3+) to arsenate (As5+) and converted some arsenosugars and non-polar arsenicals to known and/or unknown forms. Hot water (90 °C) effectively maintained the integrity of the native arsenic species and enabled analysis of the extracts with no further manipulation than filtration and dilution. Stepwise extraction of water-soluble and non-polar arsenic with hot water and a mixture of dichloromethane and methanol, respectively, resulted in sufficiently quantitative (> 75%) arsenic extraction from seafood and seaweed. Anion and cation exchange chromatographic methods were optimized for separation and quantitation of the arsenicals extracted into hot water. The non-polar arsenicals were collectively determined after digesting the extract in acid. The application of the optimum extraction and chromatographic conditions was demonstrated by analyzing certified reference materials of tuna fish tissue (BCR 627), lobster hepatopancreas (TORT-2) and oyster tissue (SRM 1566b), and a sample of hijiki seaweed. For all the matrices, good agreement (80–92%) was found between the total water-soluble arsenic and the sum of the concentrations of the chromatographed species. Limits of quantification (LOQ) were in the range 4–11 ng g−1 for 16 arsenicals.
Keywords: Arsenic; Seafood; Seaweed; Speciation; Evaluation
Speciation analysis of arsenic in seafood and seaweed: Part II—single laboratory validation of method by Mesay Mulugeta Wolle; Sean D. Conklin (5689-5702).
Single laboratory validation of a method for arsenic speciation analysis in seafood and seaweed is presented. The method is based on stepwise extraction of water-soluble and non-polar arsenic with hot water and a mixture of dichloromethane and methanol, respectively. While the water-soluble arsenicals were speciated by anion and cation exchange liquid chromatography inductively coupled plasma mass spectrometry (LC-ICP-MS), the non-polar arsenicals were collectively determined by ICP-MS after digestion in acid. The performance characteristics and broad application of the method were evaluated by analyzing eight commercial samples (cod, haddock, mackerel, crab, shrimp, geoduck clam, oyster, and kombu) and four reference materials (fish protein (DORM-4), lobster hepatopancreas (TORT-3), mussel tissue (SRM 2976), and hijiki seaweed (CRM 7405-a)) representing finfish, crustaceans, molluscs, and seaweed. Matrices spiked at three levels in duplicates were also analyzed. The stepwise extraction provided 76–106% extraction of the total arsenic from the test materials. The method demonstrated satisfactory repeatability for analysis of replicate extracts prepared over several days. The accuracy of the method was evaluated by analyzing reference materials certified for both total arsenic and a few arsenicals; the experimental results were 90–105% of the certified values. Comparison between the total water-soluble arsenic and the sum of the concentrations of the chromatographed species gave 80–92% mass balance. While spike recoveries of most arsenicals were in the acceptance range set by CODEX, a few species spiked into cod, haddock, and shrimp were poorly recovered due to transformation to other forms. After thorough investigations, strategies were devised to improve the recoveries of these species by averting their transformations. Limits of quantification (LOQ) for the extraction and quantification of 16 arsenicals using the current method were in the range 6–16 ng g−1 arsenic.
Keywords: Arsenic; Seafood; Seaweed; Speciation; Validation
Inter-laboratory validation of an inexpensive streamlined method to measure inorganic arsenic in rice grain by Rufus L. Chaney; Carrie E. Green; Steven J. Lehotay (5703-5710).
With the establishment by CODEX of a 200 ng/g limit of inorganic arsenic (iAs) in polished rice grain, more analyses of iAs will be necessary to ensure compliance in regulatory and trade applications, to assess quality control in commercial rice production, and to conduct research involving iAs in rice crops. Although analytical methods using high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) have been demonstrated for full speciation of As, this expensive and time-consuming approach is excessive when regulations are based only on iAs. We report a streamlined sample preparation and analysis of iAs in powdered rice based on heated extraction with 0.28 M HNO3 followed by hydride generation (HG) under control of acidity and other simple conditions. Analysis of iAs is then conducted using flow-injection HG and inexpensive ICP-atomic emission spectroscopy (AES) or other detection means. A key innovation compared with previous methods was to increase the acidity of the reagent solution with 4 M HCl (prior to reduction of As5+ to As3+), which minimized interferences from dimethylarsinic acid. An inter-laboratory method validation was conducted among 12 laboratories worldwide in the analysis of six shared blind duplicates and a NIST Standard Reference Material involving different types of rice and iAs levels. Also, four laboratories used the standard HPLC-ICP-MS method to analyze the samples. The results between the methods were not significantly different, and the Horwitz ratio averaged 0.52 for the new method, which meets official method validation criteria. Thus, the simpler, more versatile, and less expensive method may be used by laboratories for several purposes to accurately determine iAs in rice grain. Graphical abstractComparison of iAs results from new and FDA methods
Keywords: Inorganic arsenic (iAs) analysis; Rice; Inter-laboratory validation; Hydride generation (HG); Inductively coupled plasma-atomic emission spectroscopy (ICP-AES); ICP-MS